Antioxidants for mineral oil lubricants and compositions containing the same



dation effects on mineral lubricating oils.

Patented June 13, 1950 momnms roa maenomwam- CANTS AND THE SAME C OMTOSITION S CONTAINING Herschel G. Smith, Wallingford, and TroyL.

Can

trell, Lansdowne, Pa... and John G. Peters,

Audubon, N. 1., ore to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsyl- Vania No Drawing. Application December 21, 1948,

Serial No. 66,587 J to addition agents for mineral oil lubricants "which inhibit the oxidative deterioration of said lubricants.

In the lubrication of internal combustion engines of all types, particularly when severe operating conditions are encountered, plain mineral lubricating oils often prove unsatisfactory in service because of the oxidative deterioration of the oil, with the attendant deposition on the engine surfaces of varnish, gum or sludge. Furthermore, many lubricating oil compositions which may be highly satisfactory for the lubrication of other mechanisms have been found wholly unsuitable for use as turbine oils.

The formation of varnishes, gums and sludges on engine surfaces is due at least in part to x111; turbine oils the problem of oxidation is further aggravated, because in normal use turbine oils rapidly become contaminated with water.

It has heretofore been proposed to employ as oxidation inhibitors diamino diaryl alkanes, such as tetramethyland tetraethyldiamino diphenyl methane. However, the antioxidant potency of such compounds has not been entirely satisfactory because it is relatively low. I

It is an object of this invention, therefore, to provide an addition agent for mineral oil lubricants which will inhibit the oxidative deterioration of such lubricants.

It is a further object of this invention to provide improved mineral oil lubricant compositions which are remarkably stable against oxidation under service conditions.

These and other objects are accomplished by the present invention wherein an addition agent for mineral oil lubricants is prepared by condensing an N-diethyltoluidine, N -dimethylaniline and formaldehyde in the presence of an activated pected from the nature of the reactants, we do not obtain highly condensed, insoluble resinous products. On the contrary, when the above reactants are condensed in accordance with our invention, there are obtained light-colored condensation products which are non-resinous and which are readily soluble in mineral oils.

Any of the isomeric N-diethyltoluidines, that is, the ortho, meta and para N-diethyltoluidines, or mixtures thereof may be employed in accordance with our invention.

In performing the condensation, the reactants are mixed and heated to'a maximum temperature of 350 E. We have found that if the temperature of 350 F. is exceeded to any substantial extent, the condensation product formed tends to be resinous and insoluble. In general, the preferred temperature for the condensation ranges from 150 to 300 F.

The proportions of the reactants vary over a fairly wide range. The N-diethyltoluidine is employed in an amount of from 1 to 4 mols; N- dimethylaniline is employed in an amount of from 1 to 4 mols; and the amount of formaldehyde usedis from 1 to 4 mols. Ordinarily, it

is preferred to use from 5 to 10 per cent by clay catalyst, and recovering the condensation weight of the activated clay catalyst, based on the total weight of the reactants. However, smaller amounts, as low as'l per cent by weight, and larger amounts, as high as 20 per cent by weight, may also be employed; but larger amounts than about 10 per cent by 'weight are ordinarily not necessary.

In lieu of formaldehyde, any formaldehydeyielding compound, such as paraformaldehyde, dioxymethylene and trioxymethylene may be employed. In such case, the amount of formaldehyde-yielding compound used is based on the equivalent number of mols of formaldehyde yielded within the range of proportions of formaldehyde set forth hereinabove. Accordingly, as used in the appended claims, the term formaldehyde is intended to include formaldehyde-yielding compounds as well as formaldehyde itself.

Various activated clays may be employed in accordance with our invention. Such materials are well known in the art and comprise a natural clay, such as bentonite, fullers earth, floridin and, smectite, which has been acid treated in order to activate the clay. These materials are described in U. S. Patent 1,898,165, for example.

In preparing our new addition agents, the re-' actants and catalyst are placed into a reaction vessel which is then closed and the mixture heated with agitation under reflux until all of the formaldehyde or formaldehyde-yielding compound has'been consumed. At this time, the water which is formed as a result of the condensation is removed, preferably under vacuum,

product obtained will then be a concentrated 20 solution of the addition agent in the mineral lubricating oil.

The condensation products obtained in accordance with our invention are liquids or crystalline solids. compomtion of the condensation products is unknown, all of the three reactants enter into a final unitary product. The exact manner in which the catalyst influences the reaction is unknown. However, regardless of any theory inso volved, the use of an activated clay catalyst is an essential feature of our invention, since if the catalyst is omitted, black, insoluble, resinous condensation products may be obtained.

The following examples illustrate the preparationof our new addition agent:

Example I.Into an iron reaction vessel, there was introduced 1 mol of N-diethyl-m-toluidine,

; 2-.mols of N-dimethylaniline and 2 mols of formaldehyde in a 37% by weight aqueous solution. 40

To this mixture, there was added by weight (based on the total weight 'of the reactants) of Filtrol (anactivated montmorillonite catalyst). The vessel was closed and attached to a reflux condenser. 220' I". and refluxed for 12 hours. The condensation product was then dried by heating to 280' 1". and removing all water, both that added with the formaldehyde and formed in'the reaction. The product was then filtered. It had the 60 following properties: I

Gravity, API 9.6 Color, NPA 8.75 Neutralization No. 0.48

Example IL-ExampleI was repeated using 2 mols of N-diethyl-m-toluidine, 1 mol of N-dimethylaniline, 2 mols of formaldehyde and 10 per cent by weight of an activated diatomaceous earth. The filtered product had the following e0 properties:

Gravity, API v 8.7 Color, NPA 1.50 Neutralization No. 0.52

Example III.Anotherantioxidant was prepared under the conditions outlined in ExampleI. using 1 mol of N-diethyl-m-toluidine, 2 mols of N-dimethylaniline, 2 mole of formaldehyde and 5 per cent by weight of Filtrol (activated mont- 7o morillonite). The filtered product had the following properties:

Gravity, "API 8.2 Color, NPA 4.0

Neutralization No. 0. .5 76

While the exact nature of the chemical The mixture was then heated -to The condensation products obtained in accordance with the above disclosure from an N-diethyltoluidine, N-dimethylaniline and formaldehyde in the presence of an activated clay catalyst are excellent addition agents for mineral oil lubricants. They are readily soluble in all types of mineral oils, that isparaflinic, naphthenic or 7 mixed base mineral 011s and can be blended with mineral oils inhigh proportions to form concentrated solutions thereof, which may then be diluted down to the proportions desired inthe final mineral oil lubricant composition. As stated, our new addition agents are remarkably effective in inhibiting the oxidative deterioration of mineral oil lubricant compositions. For this purpose small amounts of our new addition agents are generally sufilcient. For example, our addition agents may be added to mineral lubricating oils in minor amounts, say from 0.001 to 1 per cent by weight on the mineral oil, suiiicient to inhibit the oxidative deterioration of the oil. Larger amounts of our new addition agents may be used if desired but it is ordinarily unnecessary to do so.

The following examples illustrate the remarkable antioxidant effects of our new addition agents. In the following examples, the base oil and the same oil blended with our new addition agents are subjected to a standard oxidation test which measures the stability of the oils to oxidation. The oxidation ,test referred to is a standard test designated ASTM D9434! T. Briefly, the test comprises subjecting the oil sample to oxygen at a temperature of 95 C." (203' 1".) in the presence of water and an iron-copper catalyst, and determining the time required to build up a neutralization number of 2. The fiow of oxygen is maintained at 3 liters per hour. The remarkably effective stability to oxidation of mineral oil lubricant compositions containing our new addition agents is illustrated by the results shown in the following examples.

Example IV.--An, improved motor lubricating oil SAE 40 was prepared by treating an SAE 40 motor oil base with 0.5 per cent by weight of the antioxidant prepared according to Example I. A comparison of the properties of the base oil and the improved oil showed:

Improved Oil Oil Gravity, 'API 30. 1 30.0 Viscosity SUV: 210 F 78.0 77.8 Color. Ni an 2.5 2.5 Neutralization No 0 01 0.02 Oxidation Test, ABTM BBQ-47'! 203 F., 3 L.

' Oxygen per Ha:

Time Oxidized, Hrs 210 3,400 Neutralization Non 2. 0 2. 0

Example V.-An improved steam turbine oil was prepared by treating a turbine oil base with 0.5 .per cent by weight of an additive prepared according to Example II. A comparison of the es properties of the base oil and improved turbine oilshowed the following:

Base Im proved Oil Gravity, Oxidation The above examples. sowthe remarkable oxidation stability imparted to mineral oil lubrlcant compositions by the use of our new addition agents. Mineral oil lubricant compositions containing our new addition agents are therefore eminently suited for use where the operating conditions are extremely severe, as in Diesel,

functionally similar compounds have been found to be either prooxidant or to show no antioxidant effects-whatsoever. For example, in our copending"applications Serial No. 66,585 and Serial No. 66,586, filed of even date herewith, we have described and claimed the condensation of N-dimethylaniline and N-diethyltoluidines, respectively, with formaldehyde in the presence of an activated clay to produce excellent antioxidants for mineral lubricating oils. Yet we have found that when xylidine, toluidine, or N-diethylaniline are individually condensed with formaldehyde in the presence of an activated clay, the resulting condensation products are not satisfactory antioxidants. It is obvious, therefore, that the type of amine used to condense with the formaldehyde is highly critical and can only be determined by experiment. The instant application is based on the discovery that mixtures of N-dimethylaniline and N-diethyltoluidines will also condense with formaldehyde in the presence of an activated clay to yield good antioxidants. Although N-diethylaniline when condensed alone with formaldehyde does not yield a satisfactory antioxidant, when mixtures of N-diethylaniline and N-dimethylaniline are condensed with formaldehyde in the presence of an activated clay, good antioxidants are obtained. This is described and claimed in our copending application Serial No. 66,588, filed of even date herewith.

While we have shown in the examples the preparation of compounded lubricating oils, our invention is not limited thereto but comprises all mineral oil lubricant compositions containing our new addition agents, such as greases and the like. If desired, other known addition agents may be incorporated into the lubricant compositions prepared in accordance with our invention. For example, pour point depressants, extreme-pressure agents, viscosity index improvers and the like may be added.

Resort may be had to such modifications and variations as fall within the spirit of the invention and the scope of the appended claims.

We claim:

1. The process of preparing an addition agent for mineral oil lubricants which comprises heating from 1 to 4 mols of an N-diethyltoluidine, 1 to 4 mols of N-dimethylaniline, and 1 to 4 mols of formaldehyde in the presence of an activated clay catalyst at a. temperature not in excess of 350 F. to condense together the three reactants, and recovering the condensation product.

2. The process of preparing an addition agent for mineral oil lubricants which comprises heating from 1 to 4 mols of an N-diethyltoluidine, 1 to 4 mols of N-dimethylaniline, and 1 to 4 mols of formaldehyde in the presence of an activated clay catalyst at a temperature of from 150 to,

to 4 mols of N-dimethylaniline, 1 to 4 mols of formaldehyde and from 5 to 10 per cent by weight on the foregoing reactants of an activated clay catalyst to a mineral lubricating oil, heating the mixture at a temperature-of from 150 to 300 F. to condense together the three reactants, and recovering a solution ofthe condensation product in the mineral lubricating oil.

4. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of N-diethyl-m-toluidine, 2 mols of N- dimethylaniline and 2 mols of formaldehyde in the presence of 5 to 10 per cent by weight of an activated clay catalyst"at a temperature from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

5. The process of preparing an addition agent for mineral oil lubricants which comprises heat I ing 2 mols of N-diethyl-m-toluidine, 1 mol of N- dimethylaniline and 2 mols of formaldehyde in the presence of 5 to 10 per cent by weight of an activated clay catalyst at a temperature from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

6. A non-resinous condensation product of from 1 to .4 mols of an N-diethyltoluidine, 1 to 4 mols of N-dimethylaniline and 1 to 4 mols of formaldehyde, said product being obtained by the process of claim 1.

7. A non-resinous condensation product of 1 mol of N-diethyl-m-toluidine, 2 mols of N-dimethylaniline and 2 mols of formaldehyde, said product being obtained by the process of claim 4. 8. A non-resinous condensation product of 2 mols of N-diethyl-m-toluidine, 1 mol of N-dimethylaniline, and 2 mols of formaldehyde, said product being obtained by the process of claim 5.

9. A lubricant composition comprising a ma.- jor amount of a mineral lubricating oil, and a minor amount, sufilcient to inhibit the oxidative deterioration of said oil, of a non-resinous condensation product of from 1 to 4 mols of an N= diethyltoluidine, 1 to 4 mols of N-dimethylaniline, and 1 to 4 mols of formaldehyde, said prodnot being obtained by the process of claim 1. l

10. A lubricant composition comprising a ma-= jor amount of a mineral lubricating oil, and a minor amount, from 0.001 to 1.0 per cent by weight of said oil, of a non-resinous condensation product of from 1 to 4 mols of N-diethyltoluidine, 1 to 4 mols of N-dimethylaniline, and 1 to 4 mols of formaldehyde, said product being obtained by the process of claim 1.

11. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, sufficient to inhibit the oxidative deterioration of said oil of a non-resinous condensation product of 1 mol of N-diethyl-m-toluidine, 2 mols of N-dimethylaniline, and 2 mols of formaldehyde, said product being obtained by the process .of claim 4.

12. A lubricant composition comprising a major amount .of a mineral lubricating oil, and a minor amount, sufiicient to inhibit the oxidative deterioration of said oil of a non-resinous con-' densation product of 2 mols of N-diethyl-m-toluidine, 1 mol of N-dimethylaniline and 2 mols of formaldehyde, said product being obtained by the process of claim 5.

13. The lubricant composition of claim 11,

wherein the condensation product ls present in an amount of 0.5 per cent by weight.

file of this patent:

4 UNITED STATES PATENTS Date Name Regal my 11, mo Vacher Aug. 23, 1932 Mattlaon Apr. 10, 1934 FOREIGN PATENTS 7 Country Date Australia Feb. 29. 1928 Great Britain Au. 12, 1920 Italy Mar. 18, 1929 

1. THE PROCESS OF PREPARING AN ADDITION AGENT FOR MINERAL OIL LUBRICANTS WHICH COMPRISES HEATFROM 1 TO 4 MOLS OF AN N-DIETHYLTOLUIDINE, 1 TO 4 MOLS OF N-DIMETHYLANILINE, AND 1 TO 4 MOLS OF FORMALDEHYDE IN THE PRESENCE OF AN ACTIVATED CLAY CATALYST AT A TEMPERATURE NOT IN EXCESS OF 350*F. TO CONDENSE TOGETHER THE THREE REACTANTS AND RECOVERING THE CONDENSATION PRODUCT. 